1. Field of the Invention
This invention relates to a device for reading information recorded on a recording medium which has a track structure such as a compact disks (DC), or a laser vision disk (LVD), etc.
2. Prior Art
Generally, recording of information onto an optical disk is carried out at a prescribed velocity (linear velocity or angular velocity). The information are recorded in succession onto spiral tracks in a state where they are put in order in time series manner. In the case of reading recorded information from such an optical disk to play back or reproduce it, a reading signal from an optical pickup is outputted as a playback signal on a real time basis.
To precisely read such record information, tracks must be correctly scanned or traced. In view of this, it has been conventionally ordinary to carry out a tracking servo control in order to modify or correct a tracking error by using means such as the three-beam method, or the push-pull method, etc.
As described above, the conventional reading device is adapted to correctly tracing the tracks by the tracking servo control. In the case where a strong impact or shock from the outside is applied thereto, however, it might take place that a light spot by the optical pickup moves or shifts to the position outside the tracking servo control range. This phenomenon is called a "track jump". Where such a track jump takes place, a light spot would move onto tracks except for tracks to be originally scanned. For this reason, a phenomenon of a sound jump appears as a playback sound. There is the possibility that such a track jump may occur not only in CD players but also in LVD players.
It is to be noted that this track jump is produced by external causes, and is therefore distinguished from an intentional or forced track jump for trick play or search.